I started costuming a little over two years ago at the at of 16. Prior to getting into costuming, I had never used spray paint. I had never hammered steel. I had never mixed Bondo, or Fiberglass. I was scared to use a rivet gun, sandpaper, and to install screws. This being said, I learned, and I adapted. You will too. -Drew

Spraypainting
Spraypainting is not as easy as it sounds. Several catastrophic things could go wrong, and it could set you back weeks. This tutorial is based on my first hand experiences, and I'll go through each medium that I can think of, and post a pictures of a finished product of mine of the said medium:

Get your piece to the way it should look. If it's resin, sand and fill necessary spots. ABS, make sure your seams are tight. Metal, make sure edges are smooth. PVC, all of the above.

If your piece is “ready” for paint, give the entire piece a thorough sanding with 320 grit sanding paper. I have found THIS grit to be the perfect grit that will allow the paint to adhere properly, but not leave sanding marks in between layers.

After your thorough sanding is completed, give a light coat of primer, color of your choice. Rattle cans should be held approximately 12-18 inches away from the piece. Any closer, and you may risk drips, which you DO NOT WANT. There may be medium still showing through, but that's okay.

After about 5 minutes, do another coat. The paint will be dry enough where it won't drip (if done properly), but it's still tacky. Repeat until happy with the outcome, and all medium is covered.

Once the piece is dry enough where you won't leave fingerprints on it, bring it into a relatively warm room. This can be a basement, an attic, or a bedroom. The warmer and dryer, the better.

Should be about 2-3 hours to cure enough to sand another coat with 320 grit.

(Optional) After the sanding, mist with a silver until satisfied with the outcome. This way here, if the piece gets bumped or rubbed, the silver shows through, and not the medium.

It is recommended to sand in between coats, but I typically don't once the coats are the exterior coats. No one wants to see sanding lines.

Resin Helmet, Metal Chest

ABS/HIPS, I don't know the difference

PVC

Sintra
I've actually never made any large props from Sintra, only small detail pieces.

The 501st Legion is a worldwide Star Wars costuming organization comprised of and operated by Star Wars fans. While it is not sponsored by Lucasfilm Ltd., it is Lucasfilm's preferred Imperial costuming group. Star Wars, its characters, costumes, and all associated items are the intellectual property of Lucasfilm.